This invention relates to coolant supply system including a pump for a filtration system for cleaning used machine tool coolant containing metal chips and recycling clean coolant back to the machine tools for reuse.
Conventional coolant pumping systems conventionally include settling tanks located below floor level which are utilized to collect dirty or contaminated coolant, pass it through a filter to a clean coolant compartment of the tank, and then pump the clean re-circulated coolant back to one or more machine tools. For example, McEwen U.S. Pat. No. 5,030,346 is one patent disclosing such a system. In this patent, the settling tank comprises two discrete compartments. One compartment is for receiving dirty coolant from multiple machine tools. A second compartment is for receiving clean coolant from a filter located between the dirty coolant compartment and the clean coolant compartment. From the clean coolant compartment, a convention centrifugal pump is operated to pump the clean filtered coolant back to one or more machine tools. Similar systems are disclosed in McEwen U.S. Pat. No. 5,154,584, Furukawa U.S. Pat. No. 5,246,336, and Nehls U.S. Pat. No. 5,279,734. In each of these patents, the dirty liquid coolant is first filtered before being supplied to a clean coolant compartment and then to a pump, such that dirty coolant never enters the pump inlet.
The dirty coolant contains metal chips or shavings produced by the machine tools during their operation. These chips are often of large size, and can clog or break the filter between the dirty coolant compartment and the clean coolant compartment. There is thus a need to reduce the size of metal chips and shavings prior to the metal pieces being supplied to a filter which, in turn, supplies clean coolant back to the machine tools.
The present invention provides a coolant supply and recycle system for cleaning used machine tool coolant and returning it to the machine tools for reuse. To this end, and in accordance with the present invention, a system is provided having a vessel or tank for receiving used coolant from one or more machine tools. The used coolant comprises contaminants including metal chips. A pump is provided in communication with the tank, and the pump is operative to withdraw used coolant including the metal chips from the tank into an inlet portion of the pump. Within the inlet, the pump includes an inducer-chopper operative to prime the pump and to chop the metal chips to effect a reduction in size prior to discharging the used coolant and chips from the pump. To accomodate the inducer-chopper, the pump impeller is recessed into an upper portion of the pump volute. The recessed impeller forces the dirty coolant with the size-reduced metal chips to the discharge portion of the pump. The pump discharge portion is connected to a filtration system for removing the sizereduced metal chips and other contaminants and supplying the clean coolant back to the machine tools. In one embodiment of the present invention, the system includes a tank having a substantially conical shaped bottom portion such that the metal chips settle in that bottom portion, and the inducer-chopper withdraws the used coolant from that bottom portion.
The present invention further provides a method for recycling coolant for at least one machine tool. The method includes operating one or more machine tools with a coolant whereby metal chips are contained in the used coolant, and this used coolant is then transferred to a dirty coolant tank. A pump having an inducer-chopper within an inlet portion thereof extracts the used coolant and metal chips into the inlet, and the inducer-chopper chops the metal chips to reduce their size. Thereafter, a recessed impeller forces the used coolant with the size-reduced chips to be discharged from the pump and supplied to a filter for removing the chips and other contaminants from the coolant. This filtered clean coolant is then recycled back to one or more machine tools for reuse.